Conventionally, in manufacturing, e.g., a device or a liquid crystal, contamination of an object to be processed, which is used for the device or the liquid crystal, by particles generated in a manufacturing process thereof has been a difficult problem to be solved. In order to reduce the contamination of the object, there has been developed a particle monitoring device for monitoring a status of a particle generation.
For example, as shown in FIG. 4, the particle monitoring device includes a laser beam source 83 having a YAG laser and a secondary harmonic wave generator 80 thereof, the laser beam source introducing a laser beam 81 into a processing apparatus 82; and a two dimensional light detector 87 as a scattered light receiver for measuring via an interference filter 86 a scattered light 85 that is generated by the laser beam 81 being scattered by particles 84 floating in a processing chamber of the processing apparatus. The laser beam 81 has, e.g., a wavelength of 532 nm, and it is shaped into a sheet form in a vertical plane to be introduced into the processing apparatus 82. When it is determined by a data processor 88 that a scattered light 85 received by the two dimensional light detector 87 is of an intensity higher than a predetermined value, the scattered light receiving time of the detector 87 is prolonged from 100 ns to 200 ns.
As described above, in the particle monitoring device using a laterally scattered light, a light receiving unit such as the two dimensional light detector 87 is disposed in a direction making about 90 degrees with respect to a projection direction of the laser beam from a light projecting unit such as the laser beam source 83. Further, in a particle monitoring device using a so-called forwardly scattered light, the light receiving unit such as the two dimensional light detector 87 is disposed in a direction making about 30˜60 degrees with respect to the projection direction of the laser beam.
(Reference document 1) U.S. Pat. No. 5,861,951
However, in case an exhaust section, which is provided in a processing chamber as a depressurized vessel to exhaust the inner space of the processing chamber, is extremely large, it is necessary to install the light projecting unit and the light receiving unit inside the exhaust section in order to increase the sensitivity to a scattered light generated by particles. Accordingly, the volume occupied by the light projecting unit and the light receiving unit in the exhaust section is increased, resulting in a decrease in an exhaust conductance to thereby deteriorate an exhaust capability of the processing apparatus.